Sacral Fracture Completeness in Lateral Compression Type 1 Pelvic Ring Injuries Has Weak Interobserver Reliability.

Objectives: To determine the agreement between fellowship-trained orthopaedic trauma surgeons in evaluating sacral fracture completeness in the setting of minimally displaced lateral compression type 1 pelvic ring injuries.

Design: Survey study.

Setting: Urban Level 1 trauma center.

Patients/participants: This study included 10 fellowship-trained orthopaedic trauma surgeons reviewing 10 cases of minimally displaced lateral compression type 1 injuries with proven occult instability (≥10 mm of fracture displacement on lateral stress radiographs). Sacral fractures were considered complete (n = 5; fracture line exiting posterior cortex of sacrum) or incomplete (n = 5).

Intervention: Participants reviewed videos of all axial computed tomography images of the sacrum and were asked if the sacral fracture was complete or incomplete.

Main Outcome Measurements: Interobserver reliability of completeness of sacral fracture.

Results: Interobserver reliability among surgeons for completeness of sacral fractures was considered to be weak (k = 0.46) with a 95% confidence interval that ranged from minimal (k = 0.37) to weak (k = 0.55). None of the 5 unstable sacral fractures that were considered to be complete garnered 100% agreement among surgeons. Agreement for each of these cases ranged from 40% to 90%. In contrast, 4 of the 5 unstable sacral fractures considered to be incomplete had 100% agreement.

Conclusions: Completeness of sacral fractures had weak interobserver reliability among fellowship-trained orthopaedic trauma surgeons. Sacral fractures that were considered incomplete by all surgeons did have occult instability. These results highlight the large potential for error created by using sacral fracture completeness as a criterion to rule out occult instability.

Level Of Evidence: Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.